Recently, filament lamps and fluorescent lamps have been replaced by a lighting device including an LED element of lower power consumption and less flicker. The lighting device may include a light source that includes the LED element, a module including drive circuit to drive the light source, and a holder in which the module is arranged (Patent Document 1). The holder supports the light source and is configured to be a heat sink to release heat generated in the LED element to an exterior. The holder can be made of a metallic material with high thermal conductivity, and it is known that the holder is generally provided by die casting with metallic material.
In a method of manufacturing the heat sink by die casting, the heat sink tends to be thick, and there is an inability to cast the holder thin. Accordingly, an amount of metallic material used to cast the holder tends to increase and can be costly. Also, if a paint or coating to finish an exterior or to improve a heat radiation rate is applied to the holder, it also tends to be costly. Not only the die casting, but also press working, similarly tends to be costly.
Furthermore, it is possible to form the holder by molding resin material instead of metallic material. However, resin has lower thermal conductivity, and it is not possible to apply a large current to the LED element. Accordingly, it is not possible to adopt this holder to a lighting device with a high-intensity LED element, and it has been adopted in a limited way to a relatively small lighting device with a low-intensity LED element.
To improve the foregoing problems, it is disclosed that an LED lighting device includes a holder made of a metallic material and a resin material (Patent Document 2).